| 摘要 |
A multi-function optical reader comprises an photosensor, such as a charge-device (CCD), and signal conditioning and processing circuitry including separate channels for handling data in different formats. A bar code processing channel digitizes the scan signal according to light and dark features using a first-derivative technique, and an OMR processing channel uses an adaptive threshold to adapt to different light conditions and provide a boundary line for digitizing light and dark features of the target scan line. A feature measurement circuit measures the widths of the light and dark regions as derived by the separate processing channels, and provides the feature measurements to a decoding system or host terminal processor. The scan rate of the optical reader can be adjusted according to the data format to be read or the level of ambient light, to avoid saturation. The optical reader can provide multiple depth-of-field zones, both internal and external to an optical reader housing. The optical reader may provide for image capture and optical character recognition.
|
